Crankshaft



cRANksHAr-'r Filed Sept. 7. 1958 2 Sheets-Sheet 2 lfm /b M l w -m w. Y N |\N MV/ Ihre Patented Oct. 8, 1940 CRANKSHAFT Torkild Valdemar Hemmingsen, Copenhagen, Denmark 1 Application September 7, 1938, Serial No. 228,867

In Denmark September 28, 1937 5 claims.

This invention relates to crankshafts of special design suitable forr multi-cylinder engines of the type operating with pistons' travelling in opposing directions, "whereby mainly internal combustion engines and more rparticularly Diesel engines are considered.

In connection with such engines `comprising two or more pistons travelling away from and towards one another within the same cylinder (or possibly in two cylinders arranged longitudinally in series)v it has hitherto been the general practice to constructthe crankshaft in such a Vmanner as to provide for each cylinder unit one crank in the centrefor the inner'piston and on each side of the said crank and staggeredapproximately 18() degrees, a crank for the outer piston or pistons, and finally on each side of the latter` cranks the main bearings. This vdesign will result in a machine of large proportions in the axial direction of the crankshaft which becomes elastic with large masses and hence' assumes a low natural coecient of oscillation affording good conditions for the creation""of harmful torsional oscillations." In orderjto remedy this complication to some extent it has been proposed to build such crankshafts with eccentric discs in place 'of the two latter cranks, but this entails, on the other hand, that the stroke for the outer piston will be. comparatively short.

In connection with smaller machines it has been proposed to construct the two exterior webs in the two cranks connected with the outer piston in the form of discs co-axial with the shaft and constituting journals for the mainbearings, whereby the shaft is forged in one piece.

This invention has for its object the utilisation of the latter principle in connection `with crankshafts for larger machines whose crankshafts do not admit of being made in one piece, but where it is of special importance to obtain a crankshaft considerably shorter than normally and much less elastic in respect of torsion, at the same time retaining the cranks for guiding the outer piston. According to this invention each main bearing journal, located between two adjacent cylinder units and common to the two adjoining cranks for the cylinder units outer pistons, is made in one with the latters adjoining crank pins, each of the said crank pins being shrunk into the adjoining web of the crank serv-V ing the inner piston. This gives a crankshaft design most suitable to the purpose and practicable and the crankshaft dimensions will be conned within reasonable limits.

In order to obtain a longer stroke for the outer piston than by normal design, without necessitating an increase in the diameteru of the main bearing journal, the journals for the cranks-adjoining a main bearing maybe executedY with a greater diameterthan-the diameter of th-pins connecting the crank webs, and arrangedeccentrically in relation to the latter. of shrinking length willbe obtained by executing lthe crank journals in question in one with the crank for thev inner piston in theform of a kind of eccentric disc, the crank thus shaped being shrunk onto the crank pins made in one with theY adjoining main bearing journals. The invention relates, furthermore, to various other designs of the"r crankshaft and to a "special arrangement of the crankshaft 'lubrication such as apparent from the followingdescription and the claims. j

The invention is illustratedin*thendrawings wherein: K y y Fig. 1v is an elevational lview of a part/of a crankshaft with its bearing `in, a formof 'execution according tothe invention, seen from one side and partly in section,

Fig. 2, an'end elevation,y partlyin section, of the parts shown inAFig. l, Figs. 3 to 6 are elevational views of four other forms of execution of a crankshaft according .toone side and partly in the invention, seen from section;

' Fig. 1 shows three cranks of whichvthe centre crank, whose crank pin is marked I, c0ntrols the inner piston .in a cylindernot-shownbut presumed to contain two pistons travelling 'in' opposite directions, of which theouter piston is controlled by the two outer cranks, e. g., by .means of a cross member and two'connecting rods arranged one on each side of the cylinder, the cranks pins being marked 6 and the journals of the latter 2. The webs 3 of the centre crank function at the same time as the one set of webs for thel two outer cranks whose other, outer webs ilare designed in the form of large discs similar to eccentric discs and which serve as bearing journals besides functioning as webs. A main bearing 3 is shown on the left hand` side of Fig. l and in this the crank 4 in question is lodged. Each main bearing journal 4 in a multicylinder machine is common to two adjoining crank sets, excepting the crank journals of the two extreme cylinder units. ACounterweights 1 may be arranged on the stroke of the centre crank, the figure showing the same made in one with the webs 3.

In the form of execution shown on Fig. 3 the An increasek side cranks journal diameter has been increased as against the corresponding journals 2 in Fig. 1, at the same time being arranged eccentrically in relation to the pins 6 on the main bearing journal 4 by means of which the crank webs 3 are afxed to the side cranks by means of shrinking. This execution ensures an increased stroke in respect of the outer piston without increase of the diameter of the main bearing journal 4.

In the form of execution shown in Fig. 4 the side crank journals 2 are made in one with the centre cranks webs 3 which gives additional.A

shrinking material for the shrinking pins B.

In the form of execution shown on Fig. 5 the side cranks journals are made in the form Aof eccentric discs 2 arranged on the shrinking pins 6, they may, as shown, be affixed 'to the centre crank webs 3 by means of bolts.

In the event that it is desired to reduce the rotating ymasses to the greatest possible extent a form of execution as shown on Fig. 6 may be utilized. Here the crank 3, I, 3 is forged in one piece,-whereas the construction otherwise corresponds with the one-shown in Fig. 1.

The comparatively large diameter and the relatively small width of the main bearing, which may `take the form of'a plain journal bearing, necessitates a specially effective supply of lubricatingoil which should aty the same time lubricatel the, three `crank journals. An oil groove encompassing the whole bearing brass which would give considerable oil losses and at the same time reduce the effective bearing area, is avoided by means of a series of interconnected holes 8 drilled in and uniformly distributed along the circumference of the main bearing journald as shown on Figs. 1 and 2. The bearingbrass 5a contains only one oil groove 9 extending over the circumference only slightly more t-han the spacing distance between the holes, i. e., in the form of execution shown, over slightly more than one-sixth of the circumferenceV which contains six holes or drillings 8. Hence at least one hole 8 will always be covered by the oil groove 9, maintaining the oil pressure in` the interconnected drillings 8. The oil is fed to the oil groove 9 through the forced lubrication passage l0, the oil being fed to the three crank journals through drillings in the crank pins and crank webs as indicated by means of the dotted lines on Fig. 1.

The lubrication passages are not shown in connection with the other forms of execution, but the lubricationl may here be effected in a similar manner. In general, details of one form of execution may be utilised for the other forms of execution shown, the examples shown and described serving merely to elucidate the various features characterising the invention. The principles of the invention may also nd utilisation in connection with machinery comprising three pistons travelling in opposing directions (one main and twov auxiliary pistons) where lthe two pistons spaced farthest apart (the auxiliary pistons) may be controlled by one set of cranks only.

` I claim:

l. A built-up crankshaft for multi-cylinder engines of the type operating with pistons traveling in opposite directions and having for each cylinder, one central main crank and two secondary outer cranks, the main crank having a pin arranged between two crank webs, each secondary crank having a pin arranged between one of said crank Webs and an outer crank web, said outer crank webs being shaped as crank discs coaxially with the shaft and serving as journals for main bearings of the shaft, each of said crank discs being integral with the vtwo adjoining secondary crank pins, and each of said crank pins being connected by means of shrinking with the adjoining crank web belonging to a main crank.

2. A built-up crankshaft according to `claim 1, in which said outer -crank pins integral with a crank disc are formed integral with journals of crank pin, said journal having a diameter lgreater than the diameter of the crank pin itself, and being arranged eccentrically in relation to the former.y

4. A crankshaft according to claim 1, in which each crank web belonging to a main crank is A connected with a journal member for the adjacent secondary crank pin, said journal member having a `diameter greater than the diameter yof the crank pin itself and ybeing arranged eccentrically in relation to the former.

5. A crankshaft according to claim 1, in which each main crank and crank pin thereof and `crank webs are made in one piece.

TORKILD VALDEMAR HEMMINGSEN. 

